shower upgrade

[paulpinky]

Hi there clever people,got a simple one for you. I need to upgrade my shower from a 7.5kw(which drips water out very slowly,Mains connected) to a 9.5kw, luckily whoever installed the original did it in 10 mm cable,and clipped it to the wall in the loft area away from the insulation.Length of cable is approx 10 meters.
My consumer unit is split and where the 32amp mcb currently sits is protected by a 80amp RCD. My question is firstly what mcb should i use or do you recomend a rcbo.secondly if i have enough capacity to upgrade to a 10.5kw shower and is there a great deal of difference in performance.This is my first time so be gentle[/quote]

 

[rebuke]

Firstly note that this work (since it involves changing the protective device) would be notifiable under Part P of the building regulations, so you either need to notify your LABC in advance (and pay their fee), or get a qualified spark who's a member of a competent person scheme in to do it.

For a 9.5kW shower, you'd normally go for a 40 or 45A MCB. The problem you may have is that you need to ensure that after diversity you aren't going to overload that 80A RCD - if it's split load and all your sockets are protected by it, then there's a chance you could.

Your cheapest option is probably just to get a spark in - it'll probably be cheaper than notifying the LABC and doing it yourself.

Edit to add that 10.5kW might be OK on your cable, but we'd need to know the exact route it takes all the way back to the CU to tell you...

 

[ban-all-sheds]

I need to upgrade my shower from a 7.5kw(which drips water out very slowly

I can understand you wanting more powerful shower, but the leak is probably easily fixed.

My question is firstly what mcb should i use

1) How many amps does a 9.5kW shower draw? http://www.kevinboone.com/electricity.html

2) Changing an MCB is notifiable. http://www.diynot.com/wiki/electrics:part-p

or do you recomend a rcbo

No - "where the 32amp mcb currently sits is protected by a 80amp RCD".

secondly if i have enough capacity to upgrade to a 10.5kw shower

http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

and is there a great deal of difference in performance

Every little helps - I'd not install less if I had the choice.

 

[paulpinky]

sorry i didn`t mean it was leaking ,i just meant that it didn`t have much power.am i correct in my understanding that a higher kw shower would give more power to my water output or am i just being naive.and yes i realise that a qualified electrician would need to install the protective device,but i`m covering my options so i know what to ask for and that i`m not ripped off unnecessarily.

 

[paulpinky]

sorry forgot to say the route of the cable goes from the cu through the floorboards,up through the floorboards in the bathroom inside the old airing cupboard, into the attic along the wall and back down into the pull cord. the cable is not clipped in the floorboards but is in the cupboard and in the attic,there is no conduit ,and is not affected by any insulation.total length 8 - 10 meters.

 

[rebuke]

In that case the 10mm^2 will be sufficient for a 10.5kW shower. One thing just to check though, you are sure it's 10mm^2 CSA, and aren't just e.g. measuring the outer width of the cable or whatever - it does seem odd to install 10mm for a 7.5kW shower, 6mm would be the normal thing to go for.

A higher kW shower will (assuming your mains pressure is not particularly low) be able to give you more water output, basically the limit on an electric shower is normally because if it goes any higher, then it couldn't get it to the temperature you want (making it hotter/colder normally just adjusts the flow over the element).

The other thing that needs checking for putting in a higher rating shower, is what the total load on your installation is, as you may be limited by this as to what rating shower you can put in.